AIDS is a fatal disease caused by human immunodeficiency virus type 1 (HIV- 1). A big stumbling block to the development of effective vaccines and therapeutics for AIDS is the lack of suitable animal model. Therefore, there is an urgent need to search for a common laboratory animal to be developed as an AIDS model. Recently two groups, one led by Kindt, T. and the other by Filice, G. independently discovered that rabbits can be infected by HIV-1 experimentally. However, infection can only be achieved by intraperitoneal injection or injection of virus producing cells in addition to high titers of HIV-1. We propose to produce transgenic rabbits expressing human CD4 gene in tissue specific manners. Those rabbits could serve as a better AIDS model than non-transgenic ones. In phase I research we will prepare the 40 kb human CD4 gene and test it in cell cultures for functional expression and susceptibility of transfected cells to HIV-1 infection. If our theory proves to be correct, we will inject the 40 kb human CD4 gene into rabbit embryos in phase II research.